The major objective of this program is to: 1) study the normal and abnormal developmental adaptation of the left and right heart in infants; 2) delineate the effect of either palliative or corrective surgery, as well as the time of the procedure, on cardiac function. All data will be obtained during routine cardiac catheterization pre- and post-operatively. Left ventricular function will be evaluated by quantifying the following variables. Left atrial and ventricular volume and left ventricular mass will be calculated according to the area- length method from biplane cineangiocardiograms (cine) filmed after injecting contrast media into the main pulmonary artery. Right ventricular (RV) volume and output will be derived according to Simpson's rule from biplane cine after injecting contrast media into the RV. Indices of contractile element velocity will be calculated from high fidelity left ventricular pressure recorded with tip transducer pressure catheter before the first biplane cineangiocardiogram. These studies will be performed before surgery and six to eighteen months after either palliative or corrective surgery. The quantitative evaluation and analysis of these variables will provide an insight into the developmental function of the left and right heart in normal and abnormal infants, and will further quantify the effect of palliative or corrective surgery on left and right ventricular function. This information should increase our current knowledge and lead to an improved care of patients with congenital heart disease.